The present invention relates to liquid storage vessels and, in particular, to an above-grade multi-sectioned cast concrete containment vessel which includes a primary, metal liquid storage container and intervening thermal liner and membrane liquid barrier.
A byproduct of society's increasing awareness of the environment and growing concerns regarding ground water contamination and the adverse effects of spilled petrochemicals (e.g. oil, gasoline etc.) has been the institution of varieties of regulatory controls. The containment tank of the present invention was developed to accommodate such regulations, especially for circumstances requiring above-grade storage of gasoline. A further purpose was to accommodate concerns of the user to cost and repair or replacement of portions of the containment system.
A variety of predecessor, below-grade storage systems have been developed for containing pressurized and non-pressurized, flammable liquids, such as gasoline, propane or natural gas. Some of such containment vessels or tanks are shown at U.S. Pat. Nos. 1,958,487; 3,151,416; 3,995,472; 4,183,221; 4,607,522; and 4,653,312. The foregoing vessels generally provide tank constructions which include a primary metal containment chamber that is surrounded by a reinforcing material, such as concrete. Intervening layers of insulators and/or liquid impermeable materials are also disclosed in various arrangements.
Numerous above-grade storage vessels are also known. Historically, much such vessels provide only a single layer of material, such as metal or concrete, and thus the concern in the event of damage to the vessel. Some vessels, however, provide a multi-layered construction that includes a primary tank, which is surrounded by a concrete or metal structure. The primary tank may or may not be integrated into the surrounding structure. U.S. Pat. Nos. 2,083,491; 2,136,390; 2,777,295; and 4,513,550 disclose various layered cast concrete containment chambers wherein the structural walls include various liquid impermeable liners.
Still other above-grade composite vessels are disclosed at U.S. Pat. Nos. 2,544,828; 3,562,977; 4,366,654; 4,372,906; 4,552,166; 4,826,644; 4,934,122; and 4,986,436. Various of the foregoing storage vessels provide a primary metal containment chamber which is surrounded by a monolithic cast concrete structure. One or more intervening membranes, which are impermeable to the contained liquid, are also provided.
Deficiencies of the foregoing monolithic storage containers is that due to the above-grade containment environment, the tank is exposed to a variety of physical dangers which can affect the life of the storage tank. Such tanks are particularly subject to potential cracking with thermal expansion/contraction; physical damage due to handling or collision from automobiles or the like; and potential corrosion from condensates which form between the steel liner and surrounding concrete assembly. Damage to any one of the components can require replacement of the entire assembly.
In preference to a monolithic assembly, a modular assembly permits replacement of one or more of the containment components in the event of damage or normal wear and tear to portions of the storage vessel. A modular construction is also more accommodating of conventional manufacturing processes, such as are used to form multi-sectioned septic tanks having open-topped bases and detachable covers.
In appreciation of the foregoing deficiencies, the present invention provides a containment vessel, which lends itself to conventional pre-cast concrete construction technology. The vessel provides an improved, environmentally friendly containment structure for storing flammable liquids, such as gasoline, propane or the like.